Photonic devices in integrated circuits generally have a less than optimal yield. For instance, Geranium (Ge) photodetectors formed using current processing technologies generally have a low yield of about 70%. Other devices such as modulators may also have low yield depending on the fabrication process. To this extent, design redundancy is needed to address this issue. Unfortunately, the use of redundant photonic devices often leads to the loss of optical power.
FIG. 1 depicts a redundant configuration of Ge photodetectors 10. An optical signal travels via a silicon (Si) waveguide to a first splitter 14, which splits the optical signal between two paths. The divided optical signal is directed by Si waveguides 12 to another set of splitters 16, where the optical signal is further divided. Each of the four portions of the optical signal is provided to a respective Ge detector 10. Thus, one-quarter of the optical power of the optical signal is provided to each of the redundant Ge detectors 10. An e-fuse 18 controlled by CMOS logic is connected to each Ge detector 10 to provide redundancy. In this example, when one of the Ge detectors 10 is nonoperational (as indicated by the “X” in FIG. 1), its corresponding fuse 18 is activated to remove the defective Ge detector 10 from the optical circuit. However, one-quarter of the optical power of the optical signal is still provided to the defective Ge detector 10 and is lost.